Features/Harfbuzz

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== Summary ==
 
== Summary ==
  
Port Pango to use Harfbuzz
+
Port Pango to use newly designed Harfbuzz
  
 
== Owner ==
 
== Owner ==
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== Benefit to Fedora ==
 
== Benefit to Fedora ==
Harfbuzz reduces the memory consumption of the desktop, since it works with mmapped fonts. Pango may also gain support for some more OpenType features in porting to  
+
Harfbuzz reduces the memory consumption of the desktop, since it works with mmapped fonts. Pango may also gain support for some more OpenType features in porting to Harfbuzz, such as BASE table support and better caret positioning in ligatures, as well as user-selected OpenType feature support.
Harfbuzz, such as BASE table support and better caret positioning in ligatures.
+
  
Further down the road (in F13), Harfbuzz will become a standalone library that will hopefully also get used by Qt, which will give us ''unified shapers'' and improved
+
Further down the road (in F13), Harfbuzz will become a standalone library that will hopefully also get used by Qt, Firefox, OpenOffice.org, and webkit, which will give us ''unified shapers'' and improved support for Indic languages across both GNOME, KDE, and OO.o.  
support for Indic languages across both KDE and Gnome.  
+
  
 
== Scope ==
 
== Scope ==
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== How To Test ==
 
== How To Test ==
#. Open a text document (TODO: point to a good multilingual document to use here) in an application that uses Pango for text rendering, e.g. gedit. Compare the text rendering between F11 and F12. There should not be any regressions.
+
#. Open a text document (For example, /usr/share/doc/pango-*/HELLO.txt) in an application that uses Pango for text rendering, e.g. gedit. Compare the text rendering between F11 and F12. There should not be any regressions.
 
#. Repeat the above with different OpenType fonts.
 
#. Repeat the above with different OpenType fonts.
#. Find the PID of your application, and look at the contents of /proc/<PID>/maps. You should see font files being mmapped.
+
#. Try the same thing with "pango-view --no-display filename".  Run it under valgrind, confirm that memory allocation is reduced between F11 and F12.
  
 
== User Experience ==
 
== User Experience ==
The most noticable change in F12 will probably be the reduced memory consumption.
+
The most noticeable change in F12 will probably be the reduced memory consumption.
 +
 
 
Beyond F12, Indic users should hopefully see improved text rendering of their languages.
 
Beyond F12, Indic users should hopefully see improved text rendering of their languages.
  
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== Contingency Plan ==
 
== Contingency Plan ==
Stay with a non-Harfbuzz-using version of Pango. Should only require a rebuild of pango itself.
+
Stay with a non-HarfBuzz-using version of Pango. Should only require a rebuild of pango itself.
  
 
== Documentation ==
 
== Documentation ==

Revision as of 18:02, 5 June 2009

Contents

Harfbuzz

Summary

Port Pango to use newly designed Harfbuzz

Owner

Current status

  • Targeted release: Fedora 12
  • Last updated: 2009-06-05
  • Percentage of completion: 20%

Harfbuzz/Pango integration happens on the harfbuzz-ng branch in the pango git repository at http://git.gnome.org/cgit/pango.

Detailed Description

HarfBuzz is an implementation of the OpenType Layout engine (aka layout engine) and the script-specific logic (aka shaping engine).


Benefit to Fedora

Harfbuzz reduces the memory consumption of the desktop, since it works with mmapped fonts. Pango may also gain support for some more OpenType features in porting to Harfbuzz, such as BASE table support and better caret positioning in ligatures, as well as user-selected OpenType feature support.

Further down the road (in F13), Harfbuzz will become a standalone library that will hopefully also get used by Qt, Firefox, OpenOffice.org, and webkit, which will give us unified shapers and improved support for Indic languages across both GNOME, KDE, and OO.o.

Scope

Only Pango needs to be changed.

How To Test

  1. . Open a text document (For example, /usr/share/doc/pango-*/HELLO.txt) in an application that uses Pango for text rendering, e.g. gedit. Compare the text rendering between F11 and F12. There should not be any regressions.
  2. . Repeat the above with different OpenType fonts.
  3. . Try the same thing with "pango-view --no-display filename". Run it under valgrind, confirm that memory allocation is reduced between F11 and F12.

User Experience

The most noticeable change in F12 will probably be the reduced memory consumption.

Beyond F12, Indic users should hopefully see improved text rendering of their languages.

Dependencies

None.

Contingency Plan

Stay with a non-HarfBuzz-using version of Pango. Should only require a rebuild of pango itself.

Documentation

None.

Release Notes

TBD.

Comments and Discussion